Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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812 FXUS64 KHUN 080219 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 919 PM CDT Tue May 7 2024 ...New NEAR TERM... .NEAR TERM... (Tonight) Issued at 919 PM CDT Tue May 7 2024 The storms that rumbled across portions of north Alabama and southern middle Tennessee have shifted east into Georgia -- with only a few light showers lingering across northeast Alabama. Observational data and the latest guidance supports more sufficient surface-based instability with SBCAPE values between 1000-2000 J/kg coupled with bulk shear values of 30-40 kts for the remainder of the overnight period. Guidance continues to support convection developing along a remnant boundary across western and middle Tennessee after Midnight which will drift ESE toward the area -- approaching northern portions of the area early Wednesday morning. The environment will support damaging wind and hail with the strongest cells (if they can make it into southern middle Tennessee and northern Alabama). Additionally, a very low (isolated) tornado threat with the strongest convection that can be sustained. Again, confidence remains low on whether this activity will make it into the area and exactly how far south this they will make it. Still, given the aforementioned environment, it is important for folks to have multiple ways to get warnings overnight in case a warning is issued for your location. && .SHORT TERM... (Wednesday through Thursday Night) Issued at 311 PM CDT Tue May 7 2024 For the rest of the day on Wednesday, low to medium (20-50%) chances of showers and storms are mostly forecast; however, not anticipating these to be severe at this time. For temperatures, it will be fairly warm tonight due to elevated moisture, with lows only dropping into the mid 60s to lower 70s. Highs Wednesday are then forecast to top out in the 80s. The "main event" in terms of severe weather will come in the form of a mesoscale convective system (MCS) traversing the Tennessee Valley Wednesday night into Thursday morning. Upper level southwest flow will continue, but more potent upper shortwaves are shown by models to ripple over the region Wednesday night into early Thursday. In addition, another low pressure system looks to develop and track over the Midwest by Wednesday evening, progressing east into the Ohio Valley by Thursday morning. Model instability will be lower overnight; but, even so, values are shown by guidance to be around 2000 J/kg. Bulk shear values range between 30-50 knots as well, with a stronger LLJ to between 35-40 knots over the region. Midlevel lapse rates are also higher, between 7-8 deg C/km along with 0-1 km SRH between 200-250 m2/s2. Therefore, the ingredients are in place for all modes of severe weather Wednesday night into Thursday morning: damaging winds, hail, and embedded tornadoes. Models have also been fairly consistent with the timing of this MCS, with it reaching northwestern Alabama around midnight and moving southeast over the local area during the overnight hours, exiting around 8AM. The Storm Prediction Center has the majority of our area in a Slight Risk (level 2/5) of severe weather, with portions of our southern middle Tennessee counties in an Enhanced Risk (level 3/5). Again, please make sure to have multiple ways to receive warnings, especially ones that will wake you up in the middle of the night! Another concern is the potential for localized flooding, especially where storms train over the same locations repeatedly. At this point, our forecast storm total rainfall ranges from 1-2 inches, with locally higher amounts possible. Turn around, don`t drown if you encounter flooded roads - find an alternate route! Once the MCS moves south of the area Thursday morning, residual chances (low to medium; 30-50%) of showers and some storms remain possible through Thursday evening. && .LONG TERM... (Friday through Monday) Issued at 427 AM CDT Tue May 7 2024 Prevailing NW flow aloft will exist across the region for much of the extended period, allowing a cooler and drier Canadian airmass to be advected deep into the southeastern CONUS. Highs will be in the 70s, with lows in the 50s, and although conditions will remain dry for most of the region, at least a couple of well- defined vorticity lobes will track southeastward across the TN Valley on Friday/Saturday, warranting a very low POP for light showers. && .AVIATION... (00Z TAFS) Issued at 836 PM CDT Tue May 7 2024 VFR conditions will continue through the remainder of the evening and into portions of the overnight. -TSRA will expand in coverage early/mid Tuesday morning, promoting MVFR conditions. Will maintain VCTS from the late morning through much of the afternoon due to the potential for redevelopment of SHRA/TSRA, especially during the 18-00z window. Amendments and AWWs may be needed if storms directly impact either terminal. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...AMP.24 SHORT TERM....26 LONG TERM....70 AVIATION...AMP